Shard-level synchronization of cloud-based data store and local file system with dynamic sharding

A method of synchronizing updates to a shared versioned file system from a local filer server, the local filer server running a local version of the shared versioned file system, comprising:

• partitioning contents of a directory into a dynamic number of shards by applying an extendible hashing function that generates a maximally-extended radix tree per a configurable maximum depth, wherein a shard is a portion of a sub-directory of the directory, the portion being less than the sub-directory as a whole, the maximally-extended radix tree having a set of leaves, wherein the shards are of predefined size based on a number of entries in the directory, wherein information about the shards is represented by shard counters corresponding to leaves of the maximally-extended radix tree, and wherein a structure of the radix tree is adjusting by tracking the shard counters and selectively applying a list of shard counter differentials;
• receiving one or more requests from the local file server to update one of more of the shards in a cloud data store;
• and
• updating one or more shards in the cloud data store in response to receipt of the requests.